Which one of the following would be true if only the left optic nerve was severed?
Correct Answer: Shining a light in the left eye would elicit the papillary reflex in both eyes
Description: Shining a light in the right eye would elicit the papillary reflex in both eyes; even though the optic nerve to the left eye was destroyed, the consensual reflex is intact because the left oculomotor nerve carries the innervation to the papillary muscles. The stimulus from the right eye crosses to the opposite side at the level of the tectum of the midbrain. However, the light in the left eye would not produce any effect because the retinal receptor would not carry the information to the brain stem. Permanent dilation would most likely occur only if the oculomotor nerve to the left eye was severed.
Category:
Ophthalmology
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